The present invention relates to a system and to a method for controlling the temperature of the engine oil of an internal combustion engine of a motor vehicle.
It is known from the prior art to use an air/engine-oil cooler, which cools the engine oil flowing therein by means of the air flow impinging on its surface, to control the temperature of the engine oil of an internal combustion engine of a motor vehicle. A problem here is that of providing a sufficiently large air impingement face. In the case of high-performance vehicles, the installation space for a correspondingly large air/engine-oil cooler, which is required, is not available.
Furthermore, German patent documents DE 199 43 002 C2, DE 102 26 928 A1 and DE 102 44 829 A1, for example, describe a coolant/engine-oil heat exchanger for controlling the temperature of the engine oil. A part of the coolant for cooling the internal combustion engine of the motor vehicle is branched off from the cooling circuit and is conducted through the coolant/engine-oil heat exchanger in order to control the temperature of the engine oil, which flows through the coolant/engine-oil heat exchanger, by means of an exchange of heat between the coolant and the engine oil. In the case of German patent documents DE 102 26 928 A1 and DE 102 44 829 A1, the coolant is branched off downstream of the internal combustion engine, i.e., the coolant for controlling the temperature of the engine oil is at a relatively high temperature. In addition, the coolant in the known systems is also conducted through the coolant/engine-oil heat exchanger by means of the coolant pump of the cooling circuit. Therefore, regulation of the cooling power of the coolant/engine-oil heat exchanger corresponding to the engine oil temperature is not possible.
An object of the present invention is to provide a system and a method for controlling the temperature of the engine oil of an internal combustion engine of a motor vehicle, which ensure suitable temperature control of the engine oil even in the case of high-performance vehicles with a limited installation space for engine oil cooling devices.
This and other objects and advantages are achieved by a system and a method according to exemplary embodiments of the present invention, including a system for controlling the temperature of the engine oil of an internal combustion engine of a motor vehicle. The system contains an engine oil circuit for controlling the temperature of the engine oil, which engine oil circuit includes the internal combustion engine and a coolant/engine-oil heat exchanger; and a coolant circuit for controlling the temperature of the internal combustion engine, which coolant circuit, in a main branch, includes the internal combustion engine, a coolant cooler and a first coolant pump. The coolant circuit also has an auxiliary branch downstream of the coolant cooler, which auxiliary branch includes the coolant/engine-oil heat exchanger and a second coolant pump.
According to the system of the exemplary embodiments, on the one hand, a coolant which is cooled in the coolant cooler is conducted through the coolant/engine-oil heat exchanger, and on the other hand, a regulable quantity of a coolant is conducted through the second coolant pump. It is hereby possible to control the temperature of the engine oil optimally corresponding to the operating state of the internal combustion engine and a temperature of the engine oil. With the system according to the invention, it is additionally the case that no great amount of installation space is required, for example, for an air/engine-oil cooler with a large air impingement face.
In one embodiment of the invention, the coolant recirculating line of the coolant/engine-oil heat exchanger opens out into the coolant supply line of the main branch upstream of the internal combustion engine. In an alternative embodiment, the coolant recirculating line of the coolant/engine-oil heat exchanger can also be conducted into a coolant recirculating line of the main branch downstream of the internal combustion engine.
In another exemplary embodiment of the invention, a control and regulating unit is also provided, which control and regulating unit controls the operation of the second coolant pump in the auxiliary branch and, in parallel, controls the operation of a fan of the coolant cooler as a function of an engine oil temperature. It is hereby possible for a temperature increase of the coolant on account of the exchange of heat in the coolant/engine-oil heat exchanger to be compensated by an increased cooling power of the coolant cooler. In addition, the control and regulating unit can control the operation of the second coolant pump in the auxiliary branch also as a function of a coolant temperature in order to prevent overheating of the coolant.
In a further embodiment of the invention, the second coolant pump is an electrically driven coolant pump which can be operated independently of the operation of the internal combustion engine and of the first coolant pump in the main branch of the coolant circuit.
In order to improve the capacity for controlling the temperature of the engine oil, the engine oil circuit also contains an air/engine-oil cooler in series with the coolant/engine-oil heat exchanger. The air/engine-oil cooler, however, on account of the above-described coolant/engine-oil heat exchanger, requires only a relatively small air impingement face in comparison with conventional systems, such that it also requires only a relatively small installation space to be made available.
According to a second aspect of the present invention, in a method for controlling the temperature of the engine oil of an internal combustion engine of a motor vehicle, the engine oil is conducted through a coolant/engine-oil heat exchanger, through which a coolant of a coolant circuit for controlling the temperature of the internal combustion engine having a coolant cooler is conducted in order to control the temperature of the engine oil by an exchange of heat between the engine oil and the coolant, in which the coolant which is cooled in the coolant cooler is conducted through the coolant/engine-oil heat exchanger as a function of a temperature of the engine oil.
As already mentioned above, on the one hand, a coolant which is cooled in the coolant cooler is conducted through the coolant/engine-oil heat exchanger, and on the other hand, a regulable quantity of a coolant is conducted through the second coolant pump. It is hereby possible to control the temperature of the engine oil optimally corresponding to the operating state of the internal combustion engine and a temperature of the engine oil. With the system according to the invention, it is additionally the case that no great amount of installation space is required for example for an air/engine-oil cooler with a large air impingement face.
In one embodiment of the invention, the coolant which is cooled in the coolant cooler is conducted through the coolant/engine-oil heat exchanger also as a function of a temperature of the coolant.
In a further embodiment of the method according to the invention, the coolant, after flowing through the coolant/engine-oil heat exchanger, is conducted into a coolant supply line upstream of the internal combustion engine, or alternatively into a coolant recirculating line downstream of the internal combustion engine.
The coolant which is cooled in the coolant cooler may be conducted through the coolant/engine-oil heat exchanger by an electrically driven coolant pump which can be operated independently of the operation of the internal combustion engine and of the first coolant pump in the main branch of the coolant circuit.
It is also possible, after the internal combustion engine is switched off in the event of an overheated coolant, for the coolant to be conducted through the coolant cooler by the electrically driven coolant pump, and at the same time for a fan of the coolant cooler to be operated, in order to avoid boiling of the coolant. The operation of the electrically driven coolant pump and of the fan of the coolant cooler is deactivated after a predetermined time has elapsed in order to conserve the vehicle electrical system voltage.
The engine oil may also be conducted through an air/engine-oil cooler.
The advantages, features and feature combinations described above and further advantages, features and feature combinations can be gathered from the following description of an exemplary embodiment of the invention with reference to the appended drawing.